Sodium silicate (Na₂SiO₃) is an inorganic compound composed of silicon dioxide and sodium oxide. It is primarily classified into the following categories based on its structure and water content:
1. Sodium metasilicate (anhydrous): Its chemical formula is Na₂SiO₃. It is commonly used in high-temperature refractory materials or adhesives.
2. Sodium metasilicate nonahydrate (Na₂SiO₃·9H₂O): Contains water of crystallization and has high solubility, making it suitable for use in the detergent and textile industries.
3. Sodium metasilicate pentahydrate (Na₂SiO₃·5H₂O): It is highly stable and is primarily used in ceramic glazes and water treatment.
4. Liquid sodium silicate (water glass): Its modulus (SiO₂/Na₂O ratio) is typically between 1.6 and 3.3. It is widely used in building reinforcement and corrosion protection.
In addition, the industry also produces sodium silicate with different properties by adjusting the modulus. For example, high modulus (>3) products have better acid resistance, and low modulus (<2) products have stronger adhesion.